This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Following are some acronyms used in the description below:
BCH broadcast channel
CSG closed subscriber group
eNB evolved NodeB (base station)
E-UTRAN evolved UTRAN (3.9 G or LTE)
GERAN GSM EDGE radio access network
GSM global system for mobile communications
LTE long term evolution
MME mobility management entity
OFDM orthogonal frequency division multiple access
PCI physical cell identifier or physical cell identity
RRC radio resource control
UMTS universal mobile telecommunications system
UTRAN UMTS terrestrial radio access network (3G)
UE user equipment (also termed mobile terminal MT)
WLAN wireless local area network
WCDMA wideband code division multiple access
Adjacent cell measurements are carried out in cell-based telecommunications systems. As known to those skilled in the art, the adjacent cell measurements are the basis for the handover and cell reselection decisions. The user equipment UE (mobile terminal), measures signal quality (such as signal strength, bit error rate BER, bit error probability BEP, or other signal quality parameters in use) from its serving cell and also from adjacent cells and reports these to the network in a measurement report. The measurement reports may be sent at regular intervals or in reply to a request/command from the network. The UE typically determines which cells are adjacent, and more narrowly which ones to measure, based on neighbor lists which in the prior art are delivered to the UEs on one or more control channels of the wireless system or by dedicated signaling. The neighbor lists contain the necessary data about the adjacent cell so that the UE can find the neighbor cells easily and efficiently with reference to the list stored in its local memory.
E-UTRAN is developing to include more network cells than previous systems, including private networks (a single cell or group of cells) which E-UTRAN terms closed subscriber group CSG network cells with home eNBs (node B's or base stations). These are also known more generically as private networks, and are available for traffic (data and/or voice) only to those UEs specifically allowed access (e.g., registered as subscribers or guests) in the private network's subscriber group. Other wireless systems (GERAN, GSM, UTRAN, WCDMA, OFDM) are also proceeding in this general direction incrementally as more functionality is shifted from the radio network controller RNC to the base stations BSs. An individual private network may cover a relatively large geographic area with multiple cells (e.g., a corporate network or a large university campus), or may consist of a single home node B. Below, the term whitelist or CSG allowed list is used to refer to a list of private (CSG) cells for which a particular UE has access rights. A CSG cell can only be accessed by UEs which belong to the CSG associated to that cell, which are member UEs or guest UEs typically. These teachings relate to the UE measurement reporting aspects of the CSG concept.
The CSG layer refers to the layer formed by the CSG cells, and the macro layer refers to the layer formed by the non-CSG cells (i.e. regular cells for which no CSG is defined). A CSG subnet refers to cells with continuous coverage associated to the same CSG. The UEs which make measurement reports are in the active state, termed in E-UTRAN as the RRC connected state, which is opposite the idle state. The RRC connected state is one in which there is a radio bearer assigned to the UE, a bearer which may or may not be maintained across a handover of the UE from one cell to another.
Current versions of the E-UTRAN Release 8 (Rel-8) specification do not address the case of UE mobility between a macro cell (any cell of the macro or non-CSG network) and CSG cells while the UE is in the RRC connected state. Reference in this regard may be had to 3GPP TS 36.331 v8.4.0 (2008-12), Radio Resource Control (RRC); Protocol Specification (Release 8). The various possible UE scenarios while in the RRC connected state must be properly planned for in order to enable UE mobility while in the RRC connected state between the macro cells and any CSG cells and vice versa.
Two co-owned references are relevant at least in part to this topic:                International Patent Application PCT/IB2008/053923, filed internationally on 25 Sep. 2008 and entitled “Closed Subscriber Group Measurement Reporting”, describes that a UE which sends to its (Macro) serving access node a measurement report of a private (CSG) cell also sends an identifier for that private cell, which in one specific embodiment may be a short tracking area ID which it knows a broadcast channel of a cell adjacent to the private cell.        International Patent Application PCT/IB2008/052457, published as WO 2009/001269, is directed to signaling between mobile terminal and network in the presence of private cells/CSGs. This document describes various means by which a UE receives an indication that a cell is private. The UE then excludes measurements of that private cell from its measurement reports sent to the macro network if that private cell is not on the UE's neighbor white list.        